Lymph node cells from rabbits immunized 6 days previously with KLH were fractionated on nylon columns. The effluent and retained cells were then characterized by various criteria. The addition of dibutyrl cAMP (DbcAMP) or cholera enterotoxin (CT) during induction with 1 and 100 micrograms KLH resulted in a 100% increase in antibody synthesis over KLH alone in both cell populations. CT and DbcAMP failed to enhance the 1 microgram KLH response of the effluent cells. Both effluent and retained cells responded to T and B mitogens and contained equal numbers of surface Ig positive cells. The removal of calcium from the medium during induction (0-24 hr) also demonstrated that induction of the antibody response was separable from the cAMP mediated enhancement of antibody synthesis. The antibody response to KLH was not enhanced by brief exposure of KLH-primed lymph node cells to DbcAMP in th absence of KLH, suggesting that some antigen-induced event(s) must occur for DbcAMP regulation. The possibility that at least one event was antigen-promoted uptake of DbcAMP was studied. It was found that 1 and 100 micrograms KLH induced maximal uptake of 3H-DbcAMP; this induced uptake was first detectable 12 hr after the addition of KLH and peaked during 24-48 hr of culture. KLH induced DbcAMP uptake required KLH reactive T lymphocytes and represented active transport of this nucleotide. The relationship of this antigen induced uptake of DbcAMP to enhancement by DbcAMP is being investigated. BIBLIOGRAPHIC REFERENCES: Regulation of the in vitro early anamnestic antibody response by exogenous cholera enterotoxin and cyclic AMP. Cook, Richard G., Abram B. Stavitsky, and Melvin D. Schoenberg. J. Immunol. 114: 426-434, 1975. Non-specific enhancement of in vitro anamnestic antibody response. Gooch, G.T. and A.B. Stavitsky. Fed. Proc. 35, p. 676, 1976.